WASHINGTON (AP) — Joe Biden is staking his presidential bid in no small part on the premise that he doesn’t need on-the-job training to lead the U.S. on a world stage that President Donald Trump has gleefully upended.

But his more liberal rivals aren’t ceding that ground.

The former vice president’s entrance into the campaign is reigniting Democratic debates over foreign policy that have largely faded to the background during the chaotic Trump era. Biden, long part of the U.S. foreign policy establishment, is being pitted against progressives more skeptical of the use of military intervention. Biden’s long record — in the Obama administration and in the Senate before that — isn’t necessarily a selling point for many progressives in the party’s base.

“It’s not going to be enough to simply have foreign policy experience and put things back to the way they were before Trump,” said Elizabeth Beavers, a longtime veteran of international non-governmental agencies and a former top adviser at Indivisible, a grassroots group on the left. “We’ve got to move the United States off the path of needless war, talking about cutting the Pentagon budget, and address the corporate greed that fuels it.”

On Thursday, it was Vermont Sen. Bernie Sanders who seemed to be leading the debate. The democratic socialist well to Biden’s left helped push an ultimately failed effort to overturn Trump’s veto of legislation withdrawing the U.S. from the bloody civil war in Yemen. As a top Sanders aide urged Biden to weigh in, the former vice president made clear that he stood with Sanders on the issue.

Biden has talked in broad strokes about international affairs in the week since he launched his campaign.

“Our standing in the world ... is at stake,” Biden said in his campaign launch. “The rest of the world, they look at us like, ‘My God,’” he added a day later on ABC’s “The View” in his first interview as a candidate.

The specifics have yet to follow.

Biden demurred in Iowa when asked about trade, saying there’d be “plenty of time” for such discussions. He avoided a question about unrest in Venezuela, only later tweeting his support for “legitimate, internationally monitored elections.” And he passed on a chance to respond to Sanders quipping that Biden had voted for the 2003 Iraq invasion, which most Democrats and some Republicans now see as a mistake.

His most specific foreign policy statement was issued through a spokesman who passed along Biden’s hope that the Senate on Thursday would override Trump on Yemen.

When Biden did talk foreign affairs while campaigning, he invited backlash. In Iowa, Biden dismissed China as a geopolitical threat. “China is going to eat our lunch? Come on, man,” he said, arguing that the world’s most populous country and second largest national economy faces more serious challenges than the U.S.

Again, Sanders pounced, tweeting that “it’s wrong to pretend that China isn’t one of our major economic competitors.”

Sanders and Massachusetts Sen. Elizabeth Warren, Biden’s two most liberal top rivals, have laid out arguably the most detailed foreign policy visions of any Democratic hopefuls and one that progressive leaders hope pushes Biden. They both give voice to the left’s argument that authoritarianism and unrest is on the rise because of corporate domination of the world economy, with the system propped up by the militarization of Western democracies.

In a speech last November, Warren warned that system will “erode America’s strength in the world.” In a subsequent essay in the journal “Foreign Affairs,” she said the status quo empowers Chinese President Xi Jinping and Russian President Vladimir Putin in one-party states. “We need to refocus our international economic policies so that they benefit all Americans, not just wealthy elites,” she said in November.

Warren has called for auditing the Pentagon budget and bringing ground troops home from Afghanistan. She also has homed in on Pentagon oversight and stepped up her activity on service-member issues since joining the Senate Armed Services Committee in 2017. She notes often that her three brothers were in the military.

Sanders regularly notes the trillions of dollars the U.S. has spent on foreign wars in the last two decades, linking the price tag to bag to his ambitious agenda for infrastructure, health care and tuition-free public college. Sanders’ aides note that he believes in a strong military that sometimes must be deployed. They say Biden’s 2003 Iraq vote should continue to be an issue because it’s illustrative of the long-standing U.S. approach that they say hasn’t actually made the nation safer.

Biden supporters say that neither policy distinctions nor philosophical disagreements among Democrats will be as important as his body of work at a time of domestic and international unease.

“You can just see that Donald Trump doesn’t have the wherewithal to build and maintain these relationships with world leaders, and Joe Biden does,” said Bill Freeman, a longtime Democratic fundraiser and friend of Biden.

Even some Biden critics agree.

Beavers, the NGO veteran, describes Biden’s record as “a mixed bag,” noting the Iraq vote, his “full-throated” support for Israeli Prime Minister Benjamin Netanyahu, and his part in an Obama administration that supported drone strikes. But she noted also instrumental role in the Iran nuclear agreement that Trump wants to scrap.

“He’s been part of what I’d call the foreign policy blob, but there’s plenty of space for him or anyone else to move away from that,” she said, adding that Biden’s “conventional” credibility could make it easier for him to offer for new approaches and explain why they aren’t “weak,” as Trump is sure to label them.

Sen. Chris Murphy, D-Conn., who began pressing for an end to U.S. support for war in Yemen as a lonely voice during the Obama years, recalled that Biden “was occasionally a foreign policy iconoclast” during his long career in the Senate. Murphy noted that Biden once floated the idea of dividing Iraq into three semi-autonomous regions.

“I don’t know that people should assume that he is going to hew to the foreign policy establishment point of view,” Murphy said of Biden in an interview. “Everyone should give him a chance to lay out his case for the world, and it might surprise people.”